Visual selective attention is a powerful cognitive brain mechanism that enables the processing of relevant stimuli while minimizing interference from irrelevant and/or distracting events. An overall goal of the proposed research is to understand the role of visual cortical ensemble activity in visual selective attention, to elucidate the detailed time course of this activity in time-varying attentional processes, and to assess their potential relevance for behavior. Advanced signal processing techniques will be employed to analyze multielectrode recordings from visual cortical areas V1, V2 and V4 of macaque monkeys. This proposal has three specific aims: (1) to investigate the dynamics of cortical processes linked to directing attention toward temporal intervals and their relationship to the requirements of behavioral tasks; (2) to investigate attention- related changes in visual cortical ensemble activity during expectation of an impending target and their relationship to attentional modulation of target-evoked activity and behavior; and (3) to investigate the distribution and timing of attention effects across areas. The proposed research is expected to provide crucial insights into the basic principles of stimulus representation and selection in visual attention and to help in understanding ensemble activity in the visual cortex that may be important for the diagnosis of psychological and psychiatric conditions that involve deficits in attention. [unreadable] [unreadable] [unreadable]